New celestial candidate revives hunt for elusive Planet Nine
Astronomers may be on the verge of identifying a mysterious object within our Solar System. Recent research suggests a possible candidate that could be the much-speculated world—Planet Nine.
Astronomers have been searching for Planet Nine, or Planet X, for years. It is a hypothetical object in our Solar System that might explain the unusual orbits of certain bodies in the Kuiper Belt, where icy celestial objects reside. A few days ago, researchers identified an object on the outskirts of the Solar System named 2017 OF201. It has an extremely elongated orbit that takes around 25,000 years to complete. According to scientists, its diameter is approximately 700 kilometres, which classifies it as a dwarf planet, similar to Pluto.
Is the new candidate the long-sought Planet Nine?
The object was discovered by a team led by astronomers from the Institute for Advanced Study’s School of Natural Sciences. It is a trans-Neptunian object (TNO), implying that its orbit around the Sun is beyond that of Neptune. The Minor Planet Center of the International Astronomical Union announced this potential new planet on 21 May, and a report by Sihao Cheng, Jiaxuan Li, and Eritas Yang describing the discovery is available in the scientific database arXiv.
The distinctiveness of 2017 OF201 lies in its extreme orbit and considerable size. Astronomers first observed this object as a bright spot using data from the Victor M. Blanco Telescope in Chile and the Canada-France-Hawaii Telescope in Hawaii. Further analysis resulted in the identification of 19 observations of this object over seven years.
Analysis revealed that its perihelion, the closest point of its orbit to the Sun, is 44.5 astronomical units (AU), and its aphelion, the furthest point, is 1,600 AU. At present, 2017 OF201 is about 90.5 AU from Earth, meaning it is 90 times more distant from us than the Sun is.
Scientists propose that the trajectory of 2017 OF201 might have been the result of a close encounter with a large planet, whose gravity propelled the object into such a remote orbit. This path means that the object spends only about 1% of its time within detectable range from Earth. Kevin Napier from the University of Michigan commented that such objects are challenging to spot because they are scarcely visible and can only be observed when they are near the Sun.
It is extremely difficult to detect
The extreme orbit, lasting roughly 25,000 years, suggests a complex history of gravitational interactions. Eritas Yang from Princeton University noted that 2017 OF201 must have had close encounters with a large planet, ejecting it into a distant orbit. Sihao Cheng from the Institute for Advanced Study’s School of Natural Sciences further suggested that there might have been multiple such encounters, with the object first being ejected into the Oort Cloud and then sent further away.
Jiaxuan Li from Princeton University pointed out that many TNOs have orbits clustered in specific orientations, but 2017 OF201 is an exception. This grouping of orbits had previously been interpreted as evidence for Planet X, which could gravitationally influence these objects. However, the presence of 2017 OF201, which does not conform to this pattern, challenges this theory.
Scientists relied solely on archival data
This discovery is pivotal for understanding the outer Solar System. The region beyond the Kuiper Belt, where the object is situated, was once thought to be empty, but the presence of 2017 OF201 indicates there could be more similar objects currently beyond detection.
Interestingly, this discovery was made possible thanks to archival data. Jiaxuan Li underscored that all the data used to identify and characterise this object were publicly accessible, demonstrating that groundbreaking discoveries are available not only to professional astronomers. Any researcher with the appropriate tools and knowledge could have made this discovery, highlighting the importance of sharing scientific resources.
